SNO's first images
9 June 1999
Within days of commencing full operation the Sudbury Neutrino Observatory (SNO) observed this striking event, shown here in an image in which the detector is seen from side. The white lines indicate geodesic support structure for the 10,000 photomultiplier tubes (PMTs) that detect light (Cherenkov radiation) emitted by charged particles produced in the interactions of neutrinos in the 1000 tonnes of heavy water within the detector. This light is emitted in a cone around the particle's path, and so forms a circular pattern when it strikes walls of the detector.
The coloured hexagons reveal the PMTs that have registered photon hits (light) in this event. The area of hits with the pink centre appears to have been caused by a muon exiting the detector. (The black area within this pattern is the hole in the PMT sphere for the chimney at the top of the acrylic heavy-water container.) This shows that the muon was headed almost straight up. The neutrino that reacted within the detector to create this muon would have to have been produced in a cosmic-ray interaction within the atmosphere on the other side of the Earth. The second ring of hits with a hollow centre is probably from a particle (a pi-meson) produced when a quark struck by the neutrino was ejected all the way from its parent proton or neutron in a nucleus in the heavy water.
Credit: SNO collaboration
For the full event display see here; and further images of this event can be accessed here (.jpg and .tiff format).
See also pictures from inside the acrylic vessel; a phototube and light concentrators; SNO under construction; and see here for a further selection of images
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